Network time synchronization, or rather, a Network Identity and Time Zone (NITZ) function, means that in the 3rd Generation Partnership Project (3GPP) protocol, a network delivers information such as a network name and/or time and a time zone to a terminal using an Over-The-Air (OTA) message, so as to help the terminal automatically synchronize with network time, date, time zone, daylight saving time, and the like. The OTA message is not mandatory, and whether to deliver the OTA message may be configured on a network side.
A network time synchronization function is supported in Global System for Mobile Communications (GSM) and Wideband Code Division Multiple Access (WCDMA) networks. However, there are still many networks that do not support the network time synchronization function. In addition, the protocol does not specify that signaling of a network and a terminal carries a flag bit indicating whether the network supports the NITZ function. Therefore, the terminal does not know whether the network supports NITZ (or time synchronization), and the terminal cannot determine, according to the network, whether to perform time synchronization.
NITZ information is delivered to a mobile phone by a network using a mobility management message (Moving Management Information or MM INFO) in an OTA message. The message is delivered after the terminal interacts with a core network. For example, the message is delivered after registration is successful, or a location update is successful, or a Short Message Service (SMS) message, a call, packet data protocol (PDP) activation, or PDP deactivation is successful.
In the prior art, in operating systems of some terminals, a setting menu generally provides an option about whether to enable automatic time synchronization. If the automatic time synchronization is enabled, the terminals synchronize with network time using an OTA message delivered by a network. If the network does not support an NITZ function, some terminals complete time and time zone synchronization by accessing a specific server using a data service.
For a current design, if a terminal can use a data service, or a network supports an NITZ function, a mobile phone can synchronize with network time. However, if neither of the two conditions exists, the terminal cannot automatically synchronize with network time and time zone.
In addition, for a method for completing time synchronization using a data service, due to an extremely high fee of a data service used in a roaming scenario, a user generally disables the data service when roaming, and consequently when roaming, the user cannot determine whether to enable an automatic time synchronization function, such that the user still needs to set time, a date, and a time zone manually.
Moreover, in the prior art, because Code Division Multiple Access (CDMA) is a synchronization system, a terminal in a CDMA network synchronizes with time of a base station by default. In addition, in some countries and regions, the terminal in the CDMA network can roam to a GSM network. Therefore, for the terminal in the CDMA network, when the terminal roams to the GSM network, if automatic time and time zone synchronization is not enabled in a setting menu, the terminal does not synchronize with network time, thereby resulting in an error in settings of time and a time zone.
In conclusion, after a terminal registers with or roams to a network, it is possible that the terminal cannot use a function of automatic time and time zone synchronization.